This invention relates in general to sand cores and in particular to an improved method for producing such a sand core.
A sand core is well known in the foundry art for forming and shaping internal cavities and openings in finished castings. The internal cavities and openings offer the advantage of allowing for a lower weight and more reliable finished casting. Oftentimes, these cavities and openings cannot be made using permanent, reusable molds and the like. Another way to produce these openings is to mold the casting around a one-time-only core which complements the configuration of the intended cavities and openings. After making the casting, the core can be destroyed or disintegrated, thereby leaving the cavities and openings in the casting available for their intended purpose.
The above one-time-only cores are commonly used in the foundry and casting industries. Manufacturers that desire a lower weight, strong finished casting typically employ sand cores in their production methods. For example, the automotive industry employs sand cores to make lower weight, fuel efficient automobile cast component parts.
Suitable materials are needed to produce the cores. The cores are typically made of materials which allow the cores to be formed into complex shapes or configurations so as to complement the cavities and openings to be created in the finished molded product. The materials must also be stable or strong enough to withstand the molding process for the application they are intended, yet weak enough so as to be easily disintegrated and removed upon completion of the molding process.
Foundry cores made of sand are produced from a variety of known methods, some of which include hot box, warm box, shell, oil sand, cement, and cold box methods. Foundry sand binders that are used for making the cores can be classified in one of two main chemical classes: organic and inorganic. Organic sand cores can employ compounds that are environmentally unfriendly. With an increased amount of concern being given to preserving the environment, the relatively environmentally friendly inorganic cores, such as those which are sand-based, grow in popularity.
A conventional inorganic sand core is formed by adding a binder to the sand to form a binder/sand mix before placing the binder/sand mix into a mold. In the mold, the binder/sand mix is shaped into a sand core having a desired shape. U.S. Pat. No. 5,711,792 to Miller discloses a foundry binder which can be used in producing inorganic sand cores. A discussed in the Miller patent, the flowability of the binder/sand mix or the ability of the binder/sand mix to properly fill the mold is an important characteristic for a properly shaped and stable sand core. The flowability of the binder/sand mix is also important to fill the molds efficiently, which promotes an acceptable production rate.
While the use of the binder provides the benefit of additional strength, it can reduce the user""s ability to handle the sand and to form intricate and complex shaped cores. Also, the temperature and humidity conditions at which the core is produced and stored can cause the core to soften and possibly lose its shape over time. Thus, it would thus be desirable to be able to produce a non-organic sand core which is durable, can be of an intricate and complex shape, yet is economical and relatively easy to produce.
This invention relates to a method for producing a core and includes the steps of: (a) providing a casting mold having a mold cavity, the casting mold including at least one first conduit and at least one second conduit; (b) providing a sand core disposed in the mold cavity; (c) providing a supply of conditioning gas to the casting mold, the conditioning gas being supplied to the casting mold through at least one of the first and second conduits; (d) providing a gas exhaust unit operatively connected to the casting mold; (e) operating the gas exhaust unit to cause the conditioning gas to be moved through the sand core; and (f) removing the sand core from the casting mold.
Other advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.